On of the great things about Firefox is the huge library of add-ons. It’s a double edged sword though as anytime you add abilities to the browser you run the risk of adding more time to each page load, especially if that add-on scans the page for content. Lets look at a flash ad blocker, the ad blocker can’t block ads until the whole page loads and it can then figure out where ads are to block. For you the end user the page won’t appear fully loaded until that whole process is complete. This isn’t a problem with just Firefox, it’s a problem with any browser that allows you to add functionality to it. To stop this fomr happening you can uninstall add-ons that you don’t use, and you can disable the add-ons you don’t use daily. Then just enable them when you need them. Firefox also just started publishing which add-ons slow down the browser the most. I was bummed to see add-ons I use on there, and I laughed when I saw the faster browser add-on on there (just proves that those lame add-ons do not increase speed). Hopefully this helps or perks your interest.
Check out the list of add-ons that slow down the browser
P.S. Thanks to everyone who made my b-day so awesome!